The invention relates to novel materials, compositions, and methods for improving the effectiveness of froth flotation beneficiation processes. Many minerals and other materials are obtained from mining and other resource recovery operations as an intimate mixture that is difficult to separate into its constituents. For example, ores as mined are often multimineralic, and contain at least one desired component, a beneficiary, and one or more other less valuable and/or desirable materials, a gangue.
In a beneficiation process, two or more materials that coexist in a mixture are separated from each other to obtain a beneficiary in a more concentrated form than that which existed in the mixture. One form of beneficiation is froth flotation separation.
In froth flotation separation of a mineral ore, the ore is finely ground (comminuted) to form a comminuted ore in the form of a particulate. The comminuted ore is slurried in a liquid medium, typically water, to make a slurry that is a sparge composition. Other components that assist in the separation of beneficiary from gangue can be included in the sparge composition, components such as collectors, modifiers, depressants, frothers (frothing agents), and/or activators.
In a process known as sparging, a gas, typically air, is bubbled through the sparge composition, and a froth forms at the surface of the sparge composition. During sparging, some materials from the ore such as targeted particles are carried up with the gas bubbles (i.e. floated) and concentrate in the froth, whereas other materials concentrate in the body of the liquid, the underflow.
The role of a collector is to assist the flotation of targeted particles in the sparge composition. The role of a depressant is to hinder or prevent the flotation of untargeted particles in the sparge composition.
The sparge composition is sparged with the gas, bubbles of which rise up out of the slurry carrying hydrophobic particles therewith and form the froth layer above the underflow. The froth layer may then be deposited on a launder. The less hydrophobic material remains behind in the slurry, thereby accomplishing the froth flotation separation.
Two common forms of flotation separation processes are direct flotation and reverse flotation. In direct flotation processes the froth comprises the beneficiary or concentrate, while in reverse flotation processes the froth comprises gangue or tailings. The object of the flotation in both forms of froth flotation is to separate and recover as much as possible of the beneficiary from the particulate material in as high a concentration of that beneficiary as possible. In froth flotation, a sparge composition is sparged to form a froth layer and an underflow. In a direct froth flotation, the froth layer comprises a concentrated beneficiary (a concentrate), and the underflow comprises tailings (concentrated gangue). In reverse froth flotation, the froth layer comprises tailings and the underflow comprises a concentrated beneficiary. In direct froth flotation, the froth can comprise more beneficiary than gangue, and the tailings can comprise more gangue than beneficiary. In reverse froth flotation, the froth can comprise more gangue than beneficiary and the tailings can comprise more beneficiary than gangue.
Froth flotation separation can be used to separate solids from solids (such as the constituents of mine ore), and liquids or semi-solids from solids (such as the separation of bitumen from oil sands).
A prerequisite for flotation separation is the liberation of particles. For flotation of mineral ores, therefore, comminuting (grinding the solids up by such techniques as dry-grinding, wet-grinding, and the like) is required to liberate minerals. Extensive grinding or comminution can result in better liberation of particles for the separation of beneficiary and gangue in a froth flotation process.
Phosphate ores commonly comprise phosphate minerals and gangue impurities such as carbonate and silicate. One phosphate mineral is apatite, which comprises PO43− and Ca2+. Apatites include hydroxyapatite (hydroxylapatite), fluorapatite, and chlorapatite, minerals which comprise in addition to phosphate anions other anions such as F−, Cl−, OH−, and/or CO32−. Among the impurities in phosphate ores are carbonates such as dolomite and/or calcite, silicates, and clays. Phosphate ores generally require beneficiation before they are used in any subsequent (downstream) processes such as phosphoric acid production. The presence of impurities in a phosphate ore, even after beneficiation, can cause considerable problems in such downstream operations. For example, presence of carbonate in a phosphate ore beneficiary can result in high sulfuric consumption and higher viscosity in phosphoric acid production from the phosphate beneficiary. Therefore, effective removal of carbonate from phosphate ore is essential for downstream phosphoric acid production from the phosphate of the ore. One of the common processes of carbonate removal is reverse froth flotation, where carbonate minerals are enriched in the froth as tailings while phosphate minerals are concentrated in the underflow.
Sulfonated fatty acids have been used since the 1980s as collectors in froth flotation beneficiation of phosphate ores. Sulfonated fatty acids have the advantage that they function as collectors over a wide range of pH, temperature and water hardness. Further, sulfonated fatty acids exhibit higher selectivity to targeted particles containing carbonate and/or silicate than non-sulfonated fatty acids. However, one disadvantage of sulfonated fatty acids when used in froth flotation is that they can cause excessive froth accompanied by reduced grade and/or recovery (yield) of beneficiary, and excessive froth can lead to downstream froth handling issues.
Although the object of froth flotation is to separate and recover as much as possible of the beneficiary in as high a concentration as possible, in such processes there is a compromise between purity of concentrate and yield of the beneficiary. Adjustment of froth flotation conditions and/or materials can produce an improvement of purity at the expense of yield or visa-versa.
In view of the above issues, it would be an advantage to provide for froth flotation improved methods and/or compositions that can be implemented in existing froth flotation installations for separation of beneficiary from ores. It would be an advantage to provide improved methods and materials therefor for obtaining better yields and better purity of beneficiaries. It would be an advantage to provide improved methods and/or compositions for froth flotation which do not cause excessive frothing during the froth flotation process accompanied by reduced grade and/or recovery (yield) of beneficiary and froth handling issues.